The invention concerns an apparatus for injection molding a bent pipe (pipe bend) made of plastic material. The pipe has a bend part with an arcuate centerline and a uniform internal cross-section, and the pipe has cylindrical connecting parts which are connected to the bend part at one or both sides of the bend part. The connecting parts have larger internal cross-sections than the bend part. The apparatus includes an injection mold which can be divided along a plane containing the arcuate centerline of the bend part into at least two outer mold portions forming a mold cavity. The injection mold includes a bend core with a pivotal member which is pivotable along the arcuate centerline of the bend part (region) and a cylindrical core which is displaceable axially along its centerline (for each connecting part). A displacement device moves of the pivotal member. The displacement device includes a bar to pivot the pivotal member, and the bar is longitudinally displaceable in the connecting part.
U.S. Pat. No. 4,184,834 discloses an apparatus for the production of a bent pipe. The pipe includes a bend part with an arcuate centerline and a uniform internal cross-section, and two enlarged connecting parts adjoining the same. A bend core portion is hingedly connected to a connecting part core portion. When the bend portion is introduced into a mold or the pipe is removed from the mold, the bend core portion must find its own way along the mold cavity or along the internal wall surface of the pipe. It is only when all of the core portions are assembled that the bend core portion is centered in the mold. A sectional plane between the cylindrical connecting part core portion and the hingedly mounted bend core portion extends into the bend part.
In the known apparatus, the connecting parts are short and wide so that removal of the bend core portion from the finished pipe can only be done by pivoting the curved bend part about the center of curvature thereof.